This invention relates to a hydraulically operated lift and, in particular, to means for preventing the lift equipment from being damaged due to overheating.
More specifically, this invention relates to a protective system for use in a hydraulic elevator.
As is well known in the art, hydraulically operated lifts and elevators are dependable pieces of apparatus that are able to efficiently raise heavy loads to substantial heights. For this and other reasons hydraulic elevators are widely used in many types of buildings. In the typical installation, the operation of the elevator is automatically controlled by means of a computer. In practice the computer is programmed to respond to normal station or floor calls as well as carry out ancillary duty functions directed toward maintaining a smooth and effective operation of the system. Such ancillary functions may include, but are not limited to, maintaining the hydraulic fluid at a constant temperature, returning the elevator automatically to a predetermined home station, such as the lobby of the building, when not in use and correctively relevelling the elevator as required.
Because this type of equipment is fully automatic, however, there exists the very real possibility that a defect or malfunction might go undetected for a relatively long period of time. In the case of certain automatic corrective functions, such as the above noted relevelling function, the equipment can in fact hide or mask a problem to such an extent that a potentially dangerous situation is created. Generally a system malfunction will cause the equipment to run excessively which, in turn, drives the temperature of the hydraulic fluid past its critical level. When this occurs, extensive equipment damage ensues and eventually a fire will result.